Conventionally, the hair is physically or chemically treated in various manners. For example, it is often shampooed, dressed with a hairbrush, dried with a hair dryer, permed, decolored, and colored with a hair color.
However, such physical or chemical treatment causes the hair to be damaged, to become bristly or to be statically charged. Accordingly, in order to maintain beautiful and healthy hair against such treatment, it is necessary to prevent the hair from being damaged and keep it soft.
For this purpose, quaternary ammonium salts are conventionally added to hair treatment compositions such as hair rinses and hair treatments.
However, the adsorption of quaternary ammonium salts on the hair is due to a mere affinity of quaternary ammonium salts for the hair, resulting in an insufficient adsorptivity. Hence, such hair treatment compositions have a resistance to swimming, sweating or the like but have a problem that they are washed away as a result of washing such as shampooing.
Recently, for basically the same purpose as the addition of quaternary ammonium salt, water-soluble macromolecules such as cationic polymers and amphoteric polymers are added to shampoos. In the case of such shampoos, a cationic/anionic composite chiefly adheres to the hair's surface, and hence the water-soluble polymer does not well penetrate into a hair, resulting in an insufficient durability of conditioning effect. There has been also a problem that the conditioning effect is rather damaged when the hair treated with such a shampoo is rinsed with the above hair treatment composition.
Accordingly, hair treatment compositions such as hair rinses are conventionally mixed with benzyl alcohol in order to promote the penetration of the water-soluble macromolecules such as cationic polymers and amphoteric polymers to the inside of a hair. It is also proposed to mix the hair treatment compositions with N-methyl- or N-ethylpyrrolidone in order to promote the penetration of quaternary nitrogen-containing cellulose ether as a sort of the cationic polymers to the inside of a hair (Japanese Patent Application Laid-open No. 3-294217).
However, in the case when the hair is treated with the hair treatment composition making use of benzyl alcohol or N-methyl- or N-ethylpyrrolidone as a penetration promoter, not only the conditioning effect immediately after treatment can not be said sufficient but also there has been a problem that the durability of conditioning effect is poor.
Oxidation hair dyes, a sort of hair treatments having been put into general use, require to make a hydrogen peroxide act on the hair under alkaline conditions when used, and hence there is a danger of causing hair damage or primary skin irritation. Accordingly, it is attempted to develop hair dyes making use of acid dyes that may less affect the scalp and the hair.
As such an attempt, diethylene glycol monoethyl ether is used in hair dyes as a penetration promoter that promotes the penetration of the acid dye into a hair. The diethylene glycol monoethyl ether is relatively well effective for keeping the hair flexible, but has a problem of insufficient dyeing properties. Accordingly, it is a recent trend to use benzyl alcohol as the penetration promoter.
In Japanese Patent Application Laid-open No. 60-228407, it is proposed to use a hair dye composition comprised of a dopa analogue, a penetration promoter and an oxidizing agent, and in U.S. Pat. No. 3,933,422, to use a hair dye composition containing a metal-containing dye and a penetration promoter.
However, as the penetration promoter, benzyl alcohol can not still be said to provide sufficient dyeing properties, can not well keep the hair flexible, and also has been problematic in view of its allergy-causative properties.
In the case of the hair dye composition disclosed in Japanese Patent Application Laid-open No. 60-228407, an oxidizing agent is used to cause the dopa analogue to form color. Hence, the color formed lacks in tone variations, and also the use of an oxidizing agent has caused a problem of hair damage.
In the case of the hair dye composition disclosed in U.S. Pat. No. 3,933,422, it may seriously cause uneven dyeing and also the dye may insufficiently penetrate into a hair. Moreover, the use of metal (chromium or cobalt) has caused problems on the feel and safety.